How DC Power Supplies Respond to Overloads
In a simple transformer-based power supply, a current overload will cause a gradual drop in voltage output (P=U x I). For example, at two times nominal current, the power supply will provide only half the normal voltage. A voltage drop may disable control components powered by the supply, which typically require at least 18 volts to operate.
Switch-mode power supplies, on the other hand, are designed to quickly shut down when the total load current reaches 110% of nominal current.
This is a feature manufacturers have designed into their products as a way to protect the power supply. The power curve of a switch-mode power supply is therefore very different. The protection that is built into a power supply usually is in the form of a quickly operating electronic switch. Most of the components under load have capacitive behavior when switching on. Current in-rush could easily exceed the range of nominal current, which can cause the power supply to shut down. Switchmode power supply manufacturers design power supplies to withstand this. If the overload condition still is present, the power supply will repeatedly try to power up and then immediately shut down - commonly known as a hiccup.